Method and device for feeding a chemical-mechanical polishing machine with a polishing product

ABSTRACT

In a chemical-mechanical polishing machine, polishing product comprising abrasive particles suspended in a reactive liquid is fed to the machine for use in a polishing operation that is divided into at least a first step and a second step. During the second step, the polishing machine is fed via a filter with a product containing fewer large particles than the product feeding the polishing machine during the first step. The feed device may be formed of two parallel lines which are provided with valves. At least one of those lines is provided with the filter.

PRIORITY CLAIM

The present application claims priority from French Application for Patent No. 05 07210 filed Jul. 6, 2005, the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to the field of chemical-mechanical polishing machines.

2. Description of Related Art

During the fabrication of integrated circuits on silicon wafers, it is necessary to carry out intermediate operations of polishing the surface of these wafers, which operations are performed using polishing machines.

Known polishing machines generally comprise a turntable bearing a polishing cloth and a rotary head that has a front face bearing the wafer and applying the latter to the polishing cloth with a controlled pressure, while a polishing product comprising abrasive particles suspended in a reactive liquid is deposited and spread over the turntable so as to be interposed between the polishing cloth and the surface of the wafer to be polished. This polishing product comes from a product source and is conveyed via a line provided with a flow control valve.

In particular, the materials generally polished may be silicon nitride, tantalum nitride, titanium nitride, single crystal silicon and other materials used in microelectronics. The abrasive particles generally used are made of silicon oxide. The reactive liquid has a pH whose value depends on the material to be polished and may contain additional species, such as surfactants and organic additives, for dispersing colloids, dissolving species during polishing or preventing corrosion of the materials.

A need exists in the art to improve the operation of chemical-mechanical polishing machines and the results obtained.

SUMMARY OF THE INVENTION

The subject of the present invention is firstly a method of feeding a chemical-mechanical polishing machine with a polishing product comprising abrasive particles suspended in a reactive liquid, for the purpose of carrying out a polishing operation on a surface of a part to be treated, during which the polishing product is interposed between this surface and a polishing plate covered with a polishing cloth.

According to an embodiment of the invention, this method comprises: dividing the polishing operation into at least a first step and a second step; and feeding the polishing machine during the second step with a product containing particles having a different particle size distribution from that of the particles contained in the product feeding the polishing machine during the first step.

According to the invention, the product feeding the polishing machine during the second step is preferably obtained by filtering the product feeding the polishing machine during the first step, retaining the particles whose size is greater than a predetermined value.

According to the invention, the method preferably comprises feeding the polishing machine with a polishing product either directly during the first step or, during the second step, and making this product pass through a particle filter that retains the large particles.

According to an embodiment of the invention, said steps correspond to predetermined thicknesses of material to be removed from the surface of the part to be treated.

The subject of the present invention is also a device for feeding a chemical-mechanical polishing machine with a polishing product comprising abrasive particles suspended in a reactive liquid.

According to an embodiment of the invention, this device includes: between a first line connected to a source of polishing product and a second line connected to the polishing machine, at least two secondary parallel lines in at least one of which a particle filter that retains the large particles is placed. It also includes means for selectively closing off one of said secondary lines so as to feed the polishing machine either directly with the product coming from the product source or with the product coming from the product source and filtered so as to retain the particles having a size greater than a predetermined value.

In an embodiment, a polishing product feeding system for a chemical-mechanical polishing machine comprises: a first line for delivering polishing product containing particles having a first particle size distribution to the chemical-mechanical polishing machine; and a second line for delivering polishing product containing particles having a second particle size distribution to the chemical-mechanical polishing machine.

In another embodiment, a chemical-mechanical polishing method comprises: delivering first polishing product containing particles having a first particle size distribution to a chemical-mechanical polishing machine; polishing with the first polishing product to remove a first thicknesses of material from the surface of a part to be treated; next delivering polishing product containing particles having a second particle size distribution to the chemical-mechanical polishing machine; and polishing with the second polishing product to remove a second thicknesses of material from the surface of a part to be treated.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the method and apparatus of the present invention may be acquired by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein:

FIG. 1 shows schematically a machine according to the invention for the chemical-mechanical polishing of a wafer;

FIG. 2 shows an enlarged partial section through this machine and the wafer;

FIG. 3 shows an abrasive particle distribution; and

FIG. 4 shows a reduced abrasive particle distribution.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows by way of example a chemical-mechanical polishing machine 1 that includes a turntable 2 of vertical axis, the upper face of which is provided with a polishing cloth 3, and a rotary head 4 of vertical axis, the lower front face of which extends only over a portion of the turntable 2, between the axis and the peripheral edge thereof.

The head 4 bears, on its front face, a wafer 5, for example an integrated circuit wafer being fabricated, and presses that surface of the wafer 5 to be polished against the polishing cloth 3 of the turntable 2.

The turntable 2 and the head 4 are respectively rotated, in a manner known per se, and a polishing product 100 is brought, in a controlled manner, onto the polishing cloth 3 at a point remote from the head 4 and is spread by a device (not shown) in such a way that a film of polishing product is established, as shown more precisely in FIG. 2, between the cloth 3 and that face of the wafer 5 to be polished, the polishing product moreover being removed.

To bring the polishing product onto the table 2, the polishing machine 1 is equipped with a feed device 6 which comprises a source 7 of polishing product, a first line 8 connected to this source, two parallel secondary lines 9 and 10 connected to this first line 8, and a second line 11 connected to these two lines 9 and 10 and emerging on the turntable 2 via means (not shown).

The parallel secondary lines 9 and 10 are equipped with shut off and optionally control valves 12 and 13, these valves being controlled by means (not shown) known per se to those skilled in the art.

The secondary line 10 is further equipped with a filter 14, for example made of cellulose.

The polishing machine 1 equipped with the feed device 6 operates and can be used in the following manner.

In general, a polishing operation comprises removing a predetermined thickness from that surface of the wafer 5 to be polished, resulting from a fixed polishing time or from an end-of-polishing detection device, using means known to those skilled in the art.

A polishing product 100 comprising abrasive particles suspended in a reactive liquid, delivered by the source 7, the particle size distribution of which is known and predetermined, is used.

This polishing operation is divided into a first step, during which the valve 12 in the secondary line 9 is in the open state and the valve 13 in the secondary line 10 is in the closed state, and a second step, during which the valve 12 in the secondary line 9 is in the closed state and the valve 13 in the secondary line 10 is in the open state.

Thus, during the first step, the polishing product coming from the source 7 is directed directly to the turntable 2, whereas during the second step the polishing product passes through the filter 14.

This filter 14 is designed and calibrated so as to retain the abrasive particles contained in the polishing product coming from the source 7 having a size greater than a predetermined value.

To give an example, the polishing operation thus performed may be such that the thickness removed during the first step is approximately between two-thirds and three-quarters of the total thickness to be removed, and the thickness removed during the second step corresponds to the rest of the thickness to be removed. In particular, if the thickness to be removed is approximately equal to 3000 angstroms, the thickness removed during the first step could be equal to about 2000 angstroms.

Thus, for example, the size of the abrasive particles contained in the polishing product 100 delivered by the source 7 may be between 40 nanometers and 2 microns. They may for example be distributed, as shown in FIG. 3, as a Gaussian curve, the x-axis of which is the particle size (Dim) and the y-axis of which is the percentages (%), the peak of which is located at about 60 nanometers on the x-axis.

The filter 14 may be calibrated so as to let through only abrasive particles having sizes of less than 0.1 microns, thus retaining the abrasive particles with sizes of greater than 0.1 microns. The particle size distribution is then established as shown in FIG. 4, as part of the Gaussian curve of FIG. 3.

Moreover, the thicknesses removed from the surface of the wafer 5 may be controlled by any known means customarily used by and known to those skilled in the art, and the valves 12 and 13 may be controlled, by any known means customarily used, according to the result of the thickness checks, so as to switch from their closed state to their open state, as mentioned above.

The polishing machine 1 makes it possible to achieve the total thickness to be removed on the surface of the wafer 5, especially in a more secure manner and to obtain a surface finish of the final polished surface of better quality, thereby contributing to the production of integrated circuits of better quality.

The present invention is not limited to the particular exemplary embodiment described above. It would in particular be possible to provide several secondary lines provided with different filters and with valves, and to selectively choose to supply the turntable with polishing product through these filters during various steps of an overall polishing operation.

Moreover, the implementation of the present invention is not limited to the machine described above and may be extended to all known polishing machines.

Other alternative embodiments are possible without departing from the scope of the appended claims.

Although preferred embodiments of the method and apparatus of the present invention have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as set forth and defined by the following claims. 

1. A method of feeding a chemical-mechanical polishing machine with a polishing product comprising abrasive particles suspended in a reactive liquid, for the purpose of carrying out a polishing operation on a surface of a part to be treated, during which the polishing product is interposed between this surface and a polishing plate covered with a polishing cloth, comprising: dividing the polishing operation into at least a first step and a second step; and feeding the polishing machine during the second step with a product containing particles having a different particle size distribution from that of the particles contained in the product feeding the polishing machine during the first step.
 2. The method according to claim 1, further comprising obtaining the product feeding the polishing machine during the second step by: filtering the product feeding the polishing machine during the first step, and retaining the particles whose size is greater than a predetermined value.
 3. The method according to either of claim 1, comprising feeding the polishing machine with a polishing product either directly during the first step or, after filtering the polishing product through a particle filter that retains relatively larger particles during the second step.
 4. The method according to claim 1, wherein said first step of the polishing operation removes a greater thicknesses of material from the surface of the part to be treated than said second step of the polishing operation.
 5. A device for feeding a chemical-mechanical polishing machine with a polishing product comprising abrasive particles suspended in a reactive liquid, comprising: a first line connected to a source of polishing product; a second line connected to the polishing machine; at least two secondary parallel lines coupled between the first and second lines; a particle filter in at least one of the first and second lines and operable to retain relatively larger particles of the polishing product; means for selectively closing off one of said secondary lines so as to feed the polishing machine either directly with the polishing product coming from the source or with the polishing product coming from the source and filtered by the particle filter which retains particles having a size greater than a predetermined value.
 6. A polishing product feeding system for a chemical-mechanical polishing machine, comprising: a first line for delivering polishing product containing particles having a first particle size distribution to the chemical-mechanical polishing machine; and a second line for delivering polishing product containing particles having a second particle size distribution to the chemical-mechanical polishing machine.
 7. The system of claim 6 wherein the polishing product comprising abrasive particles of various sizes suspended in a reactive liquid, and wherein the second particle size distribution differs from the first particle size distribution in that the second particle size distribution does not include relatively larger sized particles which are contained in the first particle size distribution.
 8. The system of claim 6 further including a polishing product delivery line which is coupled to receive product sourced from the first and second lines and deliver that product to the chemical-mechanical polishing machine.
 9. The system of claim 6 further including: a polishing product source container for delivering polishing product containing particles having the first particle size distribution to each of the first and second lines; and a particle filter associated with the second line and operable to create polishing product containing particles having the second particle size distribution from the polishing product containing particles having the first particle size distribution.
 10. A chemical-mechanical polishing method, comprising: delivering first polishing product containing particles having a first particle size distribution to a chemical-mechanical polishing machine; polishing with the first polishing product to remove a first thicknesses of material from the surface of a part to be treated; next delivering polishing product containing particles having a second particle size distribution to the chemical-mechanical polishing machine; and polishing with the second polishing product to remove a second thicknesses of material from the surface of a part to be treated.
 11. The method of claim 10 wherein the second thickness is less than the first thickness.
 12. The method of claim 10 further comprising: sourcing a polishing product containing particles having the first particle size distribution for use as the first polishing product; and filtering the sourced polishing product containing particles having the first particle size distribution to produce the second polishing product.
 13. The method of claim 10 wherein the second particle size distribution differs from the first particle size distribution in that the second particle size distribution does not include relatively larger sized particles which are contained in the first particle size distribution. 